The task of treating vehicle wheels, when already mounted with tires, requires the operator to mask the tires before cleaning or spraying, or sand blasting the wheels, so as to avoid damaging the tires.
In the past various shield devices have been proposed, which could be attached to the tires, to shield them. Examples are shown in U.S. Pat. No. 2,716,391 and 3,007,401. These devices were intended to fit around the rim of the wheel, and cover the side wall, or a portion thereof of the tire.
Other devices have been proposed which clip on to the tire itself such as shown in U.S. Pat. No. 3,141,794 for example.
These devices have suffered from various disadvantages. Some were not completely effective. In some cases, the mask did not make a tight fit around the rim, and some paint or other material could leak through, and impinge on the tire side wall. Other such devices were somewhat difficult to attach and might require two men working together to fit each shield in position.
All of these devices have suffered from the defect that vehicle tires have various different profiles around the side wall. Some tires bulge more than others. This is particularly true of, for example radial tires. Such tires tend to bulge over the rim of the wheel, and make it difficult to fit a shield in position by hand.
The profile of the side wall of the tire causes problems not merely with the fitting of a shield around the wheel rim, but also in the operation of a tensioning device for tensioning the shield around the rim.